Braathen, LR, et al. “HLA Genotypes in a Family With a Case of Homozygous C2 Deficiency and Discoid Lupus Erythematosus”. Acta Dermato-Venereologica, vol. 66, no. 5, Sept. 1986, pp. 419-22, doi:10.2340/0001555566419422.